The data analyses proposed in this study address key issues in the definition, assessment and treatment of negative symptoms in schizophrenia. We shall systematically compare the construct validity of three current scales for the assessment of negative symptoms; examine the empirical overlap among negative symptoms, depression, and neurological disorder; assess the convergent validity of different scales intended to measure blunted affect or anhedonia; and determine the effectiveness of dopamine precursor in the treatment of negative symptoms. A data set from 71 psychiatric inpatients diagnosed according to DSM-III criteria is on tape and ready for analysis. The measures, including standard structured psychiatric interviews, ratings of negative symptoms, behavioral observations, neurological examination and CT scans, intelligence testing and self-report ratings, were largely collected at three time points: washout/placebo period lasting 1-3 weeks, after approximately 5 weeks of standard treatment, and after approximately 10 weeks of standard treatment (or 5 weeks standard plus another 5 weeks of a combination of standard treatment and Sinemet). The analyses fall into four categories: (1) structural analysis of negative symptom scales, (2) comparative validity of negative symptom syndrome following a modified multitrait-multimethod procedure, (3) specific examination of the validity of blunted affect/anhedonia, and (4) repeated measures analysis of variance to examine treatment efficacy. The implications of these analyses have both practical value (with respect to immediate treatment modes) and theoretical value (with respect to the etiology of the negative symptom syndrome and its relationship to positive symptoms).